C-reactive protein increases plasminogen activator inhibitor-1 expression in human endothelial cells

C-reactive protein (CRP) is an inflammatory marker which predicts cardiovascular disease. However, it is not fully understood whether CRP has direct effects on endothelial functions and gene expression. The purpose of current study was to determine the effects and molecular mechanisms of CRP on the expression of plasminogen activator inhibitor-1 (PAI-1) in human endothelial cells. Human coronary artery endothelial cells (HCAEC) were treated with CRP at clinically relevant concentrations for different durations. PAI-1 mRNA, protein and enzyme activities were studied. The effects of CRP on MAPK p38 phosphorylation was also studied by Bio-Plex luminex immunoassay. In addition, other types of human endothelial cells isolated from umbilical vein, skin, and lung microvessels were tested. CRP significantly increased PAI-1 mRNA levels in a time- and concentration-dependent manner. The protein level and enzyme activity of PAI-1 in the supernatant of CRP-treated HCAEC cultures were significantly increased. Anti-CD32 antibody effectively blocked CRP-induced PAI-1 mRNA expression. In addition, CRP significantly increased CD32 mRNA levels and enhanced phosphorylation of MAPK p38. Furthermore, antioxidant curcumin dramatically inhibited CRP-induced PAI-1 mRNA expression. The effect of CRP on PAI-1 expression was also confirmed in other types of human endothelial cells. In conclusion, CRP significantly increased the expression of PAI-1 in HCAEC and other human endothelial cells. CRP also increased its receptor CD32 expression which may further enhance its action. CRP-induced PAI-1 expression may be mediated by oxidative stress and p38 signal pathway as antioxidant effectively blocks the effect of CRP on HCAEC.